Vapor-based coatings for antibacterial and osteogenic functionalization and the immunological compatibility.

The immobilization of biofunctional molecules to biomaterial surfaces has enabled and expanded the versatility of currently available biomaterials to a wider range of applications. In addition, immobilized biomolecules offer modified surfaces that allow the use of smaller amounts of potentially harmful substances or prevent overdose, while the exhibited biological functions remain persistently effective. Surface concentrations of chlorhexidine (CHX) (1.40±0.08×10(-9)mol·cm(-2)) and bone morphogenetic protein 2 (BMP-2) (1.51±0.08×10(-11)mol·cm(-2)) immobilized molecules were determined in this study, and their specific biological functions in terms of antibacterial activity and osteogenesis potency, respectively, were demonstrated to be unambiguously effective. Immobilization exploits the use of vapor-based poly-p-xylylenes, which exhibit excellent biocompatibility and wide applicability for various substrate materials. This technique represents a practical and economical approach for the manufacture of certain industrial products. Furthermore, a minimal degree of macrophage activation was indicated on the modified surfaces via insignificant morphological changes and low levels of adverse inflammatory signals, including suppressed production of the pro-inflammatory cytokines IL-1ß and TNF-α as well as nitric oxide (NO). The results and the modification strategy illustrate a concept for designing prospective biomaterial surfaces such that the manipulation employed to elicit targeted biological responses does not compromise immunological compatibility.

Osteogenic Surface Modification Based on Functionalized Poly-P-Xylylene Coating.

The biotechnology to immobilize biomolecules on material surfaces has been developed vigorously due to its high potentials in medical applications. In this study, a simple and effective method was designed to immobilize biomolecules via amine-N-hydroxysuccinimide (NHS) ester conjugation reaction using functionalized poly-p-xylylene coating on material surfaces. The NHS ester functionalized coating is synthesized via chemical vapor deposition, a facile and solvent-less method, creating a surface which is ready to perform a one-step conjugation reaction. Bone morphogenetic protein 2 (BMP-2) is immobilized onto material surfaces by this coating method, forming an osteogenic environment. The immobilization process is controlled at a low temperature which does not damage proteins. This modified surface induces differentiation of preosteoblast into osteoblast, manifested by alkaline phosphatase (ALP) activity assay, Alizarin Red S (ARS) staining and the expression of osteogenic gene markers, Alpl and Bglap3. With this coating technology, immobilization of growth factors onto material surface can be achieved more simply and more effectively.

Tunable coverage of immobilized biomolecules for biofunctional interface design.

The controlled coverage of immobilized biomolecules is introduced, illustrating a concept for designing biomaterial surfaces such that the extent of manipulation employed to elicit biological responses is controlled according to density changes in the underlying chemical motifs and the density of immobilized biomolecules.

Sustained immobilization of growth factor proteins based on functionalized parylenes.

Protein molecules immobilized on biomaterial surfaces are performed based on oriented conjugation or replaced mimicking peptides. The sustainable immobilization of growth factor proteins using functionalized parylene coatings is demonstrated in this study. Site-specific and nonspecific immobilization approaches are realized to conjugate bone morphogenetic protein (BMP-2). The binding affinities and conformational changes of BMP-2 are confirmed by QCM and SPR characterizations. Osteoinduction of stem cells is examined by ALP activity on the BMP-2 modified surfaces. Finally, immobilizations and equally sustained biological functions of vascular endothelial growth factor (VEGF) and a mimicking peptide of KLTWQELYQLKYKG (QK) are also examined and confirmed.

A facile approach toward protein-resistant biointerfaces based on photodefinable poly-p-xylylene coating.

A facile and versatile tool is reported that uses a photodefinable polymer, poly(4-benzoyl-p-xylylene-co-p-xylylene) to immobilize antifouling materials, such as poly(ethylene glycol), poly(ethylene glycol) methyl ether methacrylate, dextran, and ethanolamine. This immobilization process requires the polymer's photoactivated carbonyl groups, which can facilitate light-induced molecular crosslinking and can rapidly react via insertion into CH or NH bonds upon photo-illumination at 365 nm. Importantly, the process does not require additional functional groups on the antifouling materials. The immobilized fouling materials were characterized using X-ray photoelectron spectroscopy (XPS) and infrared reflection absorption spectroscopy (IRRAS), and the resulting antifouling properties were examined through protein adsorption studies on fibrinogen and bovine serum albumin at surfaces that were spatially modified using a photomask during the photochemical process. In addition, the adsorbed fibrinogen was quantitatively analyzed using a quartz crystal microbalance (QCM), and the adsorption values were reduced to 32.8 ± 4.9 ng cm(-2), 5.5 ± 3.9 ng cm(-2), 21.4 ± 4.5 ng cm(-2), and 16.9 ± 3.4 ng cm(-2) for poly(ethylene glycol) (PEG), poly(ethylene glycol) methyl ether methacrylate (PEGMA), dextran, and ethanolamine, respectively. Finally, this antifouling modification technology was demonstrated on an unconventional substrate for a stent that was modified by PEGMA at selected areas using a microscopic patterning technique during photoimmobilization. Low levels of fibrinogen and BSA adsorption were also observed at the areas where PEGMA was attached.

Vapor-based tri-functional coatings.

The tri-functional coating synthesized via CVD copolymerization is comprised of distinguished anchoring sites of acetylene, maleimide, and ketone that can synergically undergo specific conjugation reactions to render surfaces with distinct biological functions, simultaneously. In addition, these tri-functional coatings can be fabricated in a micro-structured fashion on non-conventional surfaces.